The present invention relates to a powdered material spraying device, more particularly to a powdered material spraying device having an elastic membrane with a penetrating aperture, and more specifically to a powdered material spraying device which may improve the discharge property of a powdered material from the penetrating aperture provided for the elastic membrane.
The inventors of the present invention have already proposed a minute powder spraying device utilizing an elastic membrane with a penetrating aperture in JP-A-8-161553 as powder material spraying means for quantitatively spraying a powdered material.
FIG. 19 shows a diagrammatic configuration of the spraying device. The spraying means 201 is provided for a material discharge port 202a of a powdered material storage hopper 202 for storing a powdered material so as to form a bottom of the hopper 202 and is provided with an elastic membrane 232 having a penetrating aperture 232a and with a pneumatic transport pipe T. A cover 202c is detachably and airtightly provided for a material charge port 202b of the material storage hopper 202.
The material discharge port 202a of the material storage hopper 202 is connected with the pneumatic transport pipe T so as to interpose the elastic membrane 232 in midstream of the pneumatic transport pipe T.
The penetrating aperture 232a provided for the elastic membrane 232 is a slit in this embodiment.
One end Ta of the pneumatic transport pipe T is connected to positive pulsating vibration air generation means 221. When the generation means 221 is driven, the generated positive pulsating vibration air is supplied to the pneumatic transport pipe T from the end Ta.
Next, the operations of the minute powder spraying means 201 will be explained hereinafter.
FIG. 20 is a diagrammatic explanatory view how the elastic membrane 232 of the spraying means 201 operates.
For spraying a fixed amount of powdered material from the other end Tb of the pneumatic transport pipe T by means of the spaying means 201, a powdered material is stored in the material storage hopper 202. Then the cover 202c is airtightly attached on the material charge port 202b of the powder material storage hopper 202.
Next, a positive pulsating vibration air is supplied to the pneumatic transport pipe T by driving the positive pulsating vibration air generation means 221.
According to the spraying means 201, when the positive pulsating vibration air is supplied to the pneumatic transport pipe T, the pressure in the pneumatic transport pipe T increases at a peak amplitude of the pulsating vibration air, and the elastic membrane 232 is deformed to curve its center upwardly. In this case, the penetrating aperture 232a is shaped like a letter V in such a manner that the top is opened seen in section. A part of the powdered material stored in the storage hopper 202 falls in the V-shaped penetrating aperture 232a (see FIG. 20a).
As the positive pulsating vibration air supplied to the pneumatic transport pipe T is directed to the valley of the amplitude and the pressure in the pneumatic transport pipe T is gradually reduced, the elastic membrane 232 returns to its original shape from the upwardly curved shape because of its restoring force. At the same time the V-shaped aperture 232a is returned to its original shape and the powdered material dropped in the V-shaped aperture 232a is caught in the aperture 232a (see FIG. 20b).
Then the positive pulsating vibration air supplied to the pneumatic transport pipe T comes to be its valley of the amplitude and the pressure in the pneumatic transport pipe T is reduced, the elastic membrane 232 is elastically deformed with the center curved downwardly. In this time the penetrating aperture 232a forms like a reverse V-shape in such a manner that the lower end is opened seen in section, and the powdered material caught in the aperture 232a falls in the pneumatic transport pipe T (see FIG. 20c).
The powdered material dropped in the pneumatic transport pipe T is mixed with and dispersed in the positive pulsating vibration air supplied in the pipe T.
The dropped material in the pipe T is pneumatically transported to the other end Tb of the pipe T to be sprayed with the positive pulsating vibration air therefrom.
The vibration of the elastic membrane 232 of the minute powder spraying means 201 depends on the positive pulsating vibration air supplied in the pipe T. The amount of powdered material supplied via the penetrating aperture 232a to the pneumatic transport pipe T is primary determined by the vibration of the elastic membrane 232. Therefore, a fixed amount of powdered material is discharged to the pneumatic transport pipe T as long as the positive pulsating vibration air supplied to the pneumatic transport pipe T is constant.
A positive pulsating vibration air, not a constant air flow, is designed to be supplied to the pneumatic transport pipe T. Therefore, the powdered material in the pneumatic transport pipe T doesn""t cause accumulation and pinhole, which have been seen when a powdered material is pneumatically transported at a steady air flow in the pipe T to the other end Tb.
Accordingly, almost all of the powdered material supplied to the pneumatic transport pipe T via the penetrating aperture 232a of the elastic membrane 232 is sprayed from the other end Tb of the pneumatic transport pipe T.
The powder material spraying means 201 has a beneficial effect such that a fixed amount of powdered material can be always sprayed from the other end Tb of the pneumatic transport pipe T as long as the positive pulsating vibration air supplied in the pipe T is constant. Furthermore, the spraying means 201 has a beneficial effect wherein the concentration of the powdered material sprayed from the other end Tb of the pneumatic transport pipe T can be easily changed because it can be varied depending on the positive pulsating vibration air supplied from the one end Ta of the pipe T.
However according to this spraying means 201, air is fed in the powdered material storage hopper 202 from the pneumatic transport pipe T through the penetrating aperture 232a of the elastic membrane 232, and the powdered material is discharged from the storage hopper 202 through the penetrating aperture 232a of the elastic membrane 232.
The air flow to the storage hopper 202 from the pneumatic transport pipe T and the discharge of the powdered material in the pneumatic transport pipe T from the hopper 202, both of which are done via the penetrating aperture 232a of the elastic membrane 232, utilize reverse air flows respectively. The pressure in the pneumatic transport pipe T is higher than that in the storage hopper 202 at a time of driving. The elastic membrane 232 is apt to expand into a direction of the storage hopper 202 (upwardly) till a balanced condition immediately after driving. Therefore, the amount of the powdered material discharged from the penetrating aperture 232a of the elastic membrane 232 is reduced so that the amount of material sprayed from the other end Tb of the pneumatic transport pipe T is subject to be reduced.
It has been found that when the charge amount of powdered material in the storage hopper 202 is varied, the amount of powdered material sprayed from the other end Tb of the pneumatic transport pipe T has been varied, thereby deteriorating its quantitativeness.
According to the minute powder spraying means 201, the quantitativeness of powdered material sprayed from the other end Tb of the pneumatic transport pipe T depends on the vertical vibration pattern of the elastic membrane 232. Therefore, even though the positive pulsating vibration air is accurately generated, the elastic membrane 232 doesn""t execute an accurate reproductive movement for the positive pulsating vibration air in case that the elastic membrane 232 having the penetrating aperture 232a provided at the discharge port 202a of the storage hopper 202 isn""t uniformly stretched with an appropriate tensile, thereby deteriorating the quantitativeness of the powdered material sprayed from the other end Tb of the pneumatic transport pipe T.
For ensuring the quantitativeness of powdered material sprayed from the other end Tb of the pipe T of the spraying means 201, a problem exists because functions of the means 201 can""t be brought out well when the elastic membrane 232 is slackly attached.
Furthermore, if such means 201 is used for a long time, the elastic membrane 232 gradually comes to be slack because of the vibration and the function of the means 201 is deteriorated with time.
When the powdered material stored in the storage hopper 202 is directly discharged in the pneumatic transport pipe T via the penetrating aperture 232a of the elastic membrane 232, if large particles of powdered or granular material are contained in the stored material in the hopper 202, such large particles are pneumatically transported in the transport pipe T and are sprayed from the other end Tb.
There remains a room of improvement so as not to spray such large particles from the other end Tb of the pneumatic transport pipe T while keeping the quantitativeness of powdered material sprayed from the other end Tb of the pipe T in order to utilize the means 201 as a lubricant spray device for spraying a lubricant on each surface of upper punches, lower punches, and dies of an external lubrication type tabletting machine which requires the quantitativeness and evenness of the lubricant particle size.
The present invention has been proposed in order to solve the above-mentioned problems and to provide a powdered material spraying device superior in the discharge property and quantitativeness of the powdered material executed by means of a penetrating aperture 232a of an elastic membrane 232. The present invention has also been proposed to provide a powdered material spraying device wherein an elastic membrane can be equipped at a material discharge port of a powdered material storage hopper easily, at an appropriate tensile strength, and uniformly. Furthermore, the present invention has been proposed to provide a powdered material spraying device which is more improved 60 as not to spray large particles of the powdered material while keeping the quantitativeness of powdered material sprayed from one end Tb of a pneumatic transport pipe T.
According to the powdered material spraying device as set forth in claim 1, powdered material spraying device includes; a powdered material storage hopper for storing a powdered material, a quantitative spraying device provided for a material discharge port of the powdered material storage hopper via a material feed valve. A cover is detachably and airtightly provided for the material discharge port of the powdered material storage hopper. The quantitative spraying device includes a cylindrical body with openings at the top and the end respectively, the cylindrical body being airtightly connected with the material discharge port of the powdered material storage hopper, an elastic membrane with a penetrating aperture provided so as to form a bottom of the cylindrical body at its lower opening end, and a dispersion chamber connected under the lower opening end of the cylindrical body via the elastic membrane. The dispersion chamber includes a pulsating vibration air supply port for supplying a positive pulsating vibration air therein, and a discharge port connected with a conduit for pneumatically transporting the powdered material to a desired place by means of the positive pulsating vibration air. The powdered material is discharged into the dispersion chamber via the penetrating aperture when the elastic membrane is vibrated up and down by the positive pulsating vibration air supplied to the dispersion chamber from the pulsating vibration air supply port and is mixed with the positive pulsating vibration air. A bypass pipe is connected between the cylindrical body and the dispersion chamber.
According to this powdered material spraying device, an air communication passage between the cylindrical body and the dispersion chamber is comprised of two lines: the penetrating aperture provided for the elastic membrane and the bypass pipe by connecting the bypass pipe between the cylindrical body and the dispersion chamber.
It isn""t sure at the present moment how the installation of the bypass pipe other than the penetrating aperture of the elastic membrane as an air passage between the cylindrical body and the dispersion chamber acts on improving the discharge efficiency of the powdered material into the dispersion chamber which is executed through the penetrating aperture of the elastic membrane. However, the inventors of the present invention think that the bypass pipe contributes to improve the discharge efficiency of the powdered material in the dispersion chamber because of the following operational principles.
When the air communication passage between the cylindrical body and the dispersion chamber is the penetrating aperture only, an air flow to equalize the pressure in the cylindrical body and that in the dispersion chamber is caused only via the penetrating aperture.
A positive pulsating vibration air is then supplied to the dispersion chamber, air flows from the dispersion chamber to the cylindrical body through the aperture when the pressure in the dispersion chamber is higher than that in the cylindrical body. If the pressure in the dispersion chamber is lower than that in the cylindrical body, air flows from the cylindrical body to the dispersion chamber through the penetrating aperture.
Accordingly, it takes a long time to balance the pressures in the cylindrical body and in the dispersion chamber and the elastic membrane is apt to expand into the cylindrical body (upwardly). As a result, the vibration of the positive pulsating vibration air tends to be smaller so that the expansion and contraction of the penetrating aperture of the elastic membrane gets small. The amount of discharged powdered material via the penetrating aperture may be reduced immediately after driving the device till the pressures above and under the elastic membrane are balanced.
Contrary in the present invention, the air communication passage has two lines consisting the penetrating aperture of the elastic membrane and the bypass pipe so that the air can flow between the cylindrical body and the dispersion chamber via an available line.
When the positive pulsating vibration air is supplied to the dispersion chamber, the pressure in the cylindrical body and that in the dispersion chamber are balanced at once, enabling the elastic membrane to vibrate up and down with substantially an equal amplitude with its original extended position as a neutral position, thus achieving the reproducibility and responsibility of the vibration.
As a result, it is considered that the discharge of the powdered material via the penetrating aperture of the elastic membrane can be executed suitably.
According to the powdered material spraying device as set forth in claim 2, the elastic membrane is provided by means of an elastic membrane installation device between a lower part of the cylindrical body and an upper part of the dispersion chamber. The elastic membrane installation device comprises a pedestal with a hollow part, a push-up member with a hollow part provided so as to rise on a surface of the pedestal and a presser member with a hollow part which is a little larger than an outer circumference of the push-up member. The pedestal has a V-groove outside of the hollow part to be the outside of the outer circumference of the push-up member so as to annularly surround the hollow part of the pedestal and the presser member has an annular V-shaped projection on its surface casing the pedestal so as to be incorporated with the V-groove provided on the surface of the pedestal. The push-up member is placed on the surface of the pedestal, and then the elastic member is placed thereon. The presser member is fastened against the pedestal so as to cover both the push-up member and the elastic membrane, therefore the elastic membrane is kept to be extended from its center to its periphery by pushing up the elastic membrane into the presser member by means of the push-up member. Thus extended periphery of the elastic membrane by the push-up member is held between a periphery (inclined plane) of the push-up member and a plane forming the hollow of the presser member and also between the V-groove on the surface of the pedestal and the V-shaped projection on the surface of the presser member facing the pedestal. The bottom of the pedestal is provided above the dispersion chamber and under the presser member is provided at the lower end of the cylindrical body.
When the elastic membrane is placed on the push-up member on the pedestal of the elastic membrane installation means and is fastened by the presser member to the pedestal, the elastic membrane is pushed upwardly against the presser member by the push-up member. As a result, the elastic membrane is extended from its center to its periphery by being pushed upwardly into the presser member.
At first, the elastic membrane extended by the push-up member is inserted between the V-groove on the pedestal surface and the V-shaped projection of the surface of the presser member facing the pedestal via a space between the periphery (inclined surface) of the push-up member and a surface (inner surface) forming the hollow part of the presser member.
As the presser member is further fastened against the pedestal, the elastic membrane is held between the periphery (inclined surface) of the push-up member and the surface (inner surface) forming the hollow of the presser member while being pushed upwardly to the presser member with the push-up member. The inserted portion between the V-groove on the pedestal surface and the V-shaped projection on the presser member""s surface facing the pedestal when the elastic member is extended from its center to its periphery by being pushed up into the presser member by the push-up member is held between the V-groove and the V-shaped projection.
According to the elastic membrane installation means, the elastic membrane can be strained by a simple operation such that the elastic membrane is placed on the push-up member on the pedestal and the presser member is fastened to the pedestal.
The push-up member of the powdered material spraying device of the present invention may have an inclined plane extending from top to bottom at its periphery seen in section.
As the inclined plane is provided for the periphery of the push-up member, the extended portion from its center to its periphery of the elastic membrane pushed up to the presser member is easily moved between the V-groove formed like a ring on the pedestal and the V-shaped projection formed like a ring on the surface of the presser member facing the pedestal.
As mentioned above, the elastic membrane can be strained by a simple operation such that the elastic membrane is placed on the push-up member on the pedestal and the presser member is fastened to the pedestal.
Furthermore, as the presser member is further fastened to the pedestal, the space between the inclined plane at the periphery of the push-up member and the inner surface of the hollow part of the presser member is gradually narrowed. Therefore, the elastic membrane is tightly held between the periphery (inclined plane) of the push-up member and the inner surface of the hollow of the presser member so that the elastic membrane doesn""t get slack after the presser member is fastened to the pedestal.
Accordingly, if the elastic membrane is stretched with the elastic membrane installation means when a diaphragm is stretched for an instrument or an elastic membrane of a powdered material spraying device is stretched, the elastic membrane doesn""t get slack during operation, enabling the device to keep an accurate operation for a long time.
The pulsating vibration air supply port of the powdered material spraying device of the present invention may be provided at the lower part of the dispersion chamber in a substantially tangential direction against an internal circumference of the dispersion chamber, and the discharge port may be provided at the upper part of the dispersion chamber in a substantially tangential direction against the internal circumference of the dispersion chamber.
According to the powdered material spraying device, a positive pulsating vibration air is introduced from the lower part of the dispersion chamber, that is approximately from a tangential direction and is discharged from the upper part of the dispersion chamber, that is approximately into a tangential direction. The positive pulsating vibration air is swirled like a whirlpool from bottom to top in the dispersion chamber.
The dispersion chamber has a particle size classification function like a cyclone by means of the positive pulsating vibration air swirling upwardly in the dispersion chamber.
Therefore, if large agglomerated particles of the powdered material are discharged in the dispersion chamber via the penetrating aperture of the elastic membrane, they keep swirling in the bottom of the dispersion chamber so that such large particles aren""t sprayed from the other end of the pipe.
Such a powdered material spraying device can spray a quantitative amount of powdered material with even particle size from the other end of the pipe.
Furthermore, the large particles are caught in the swirling flow of the positive pulsating vibration air in the dispersion chamber so as to be pulverized into smaller particles. Thus pulverized particles into a predetermined particle size are discharged outside of the dispersion chamber riding the swirling flow of the positive pulsating vibration air so that the powdered material with a large particle size is hardly accumulated in the dispersion chamber.